Thread: pgsql: Handle lack of DSM slots in parallel btree build.

Handle lack of DSM slots in parallel btree build.

If no DSM slots are available, a ParallelContext can still be
created, but its seg pointer is NULL.  Teach parallel btree build
to cope with that by falling back to a regular non-parallel build,
to avoid crashing with a segmentation fault.

Back-patch to 11, where parallel CREATE INDEX landed.

Reported-by: Nicola Contu
Reviewed-by: Peter Geoghegan
Discussion: https://postgr.es/m/CA%2BhUKGJgJEBnkuODBVomyK3MWFvDBbMVj%3Dgdt6DnRPU-5sQ6UQ%40mail.gmail.com

Branch
------
REL_11_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/2c56b3ac436db2d24aa11bdd22f45becf2030607

Modified Files
--------------
src/backend/access/nbtree/nbtsort.c | 9 +++++++++
1 file changed, 9 insertions(+)